Sickle cell HbSD is a form of sickle cell disease (SCD) that involves two different types of abnormal haemoglobin proteins. Haemoglobin is a protein contained in red blood cells that helps oxygen bind to red blood cells so that it can be carried throughout the body. SCD refers to a group of genetic disorders that causes sickling of the red blood cells and many health complications as a result. While healthy red blood cells are normally round, sickling causes them to become shaped like a crescent moon and to be sticky and hard.
SCD can be caused by a variety of abnormal haemoglobin proteins. Someone with HbSD has one copy of the haemoglobin gene that encodes for the haemoglobin “S” and one copy of the haemoglobin gene that encodes for the haemoglobin “D” protein. People with HbSD typically deal with many of the symptoms of SCD, but the risk of complications from SCD is much lower than in people with two copies of the haemoglobin “S” gene.
The main symptoms of sickle cell HbSD include:
Many children are diagnosed with SCD as newborns, before they leave the hospital. If your child was not screened for SCD as a newborn and is showing symptoms, such as a fever, potential infection, or even signs of a stroke, take your child to the doctor right away.
Sickle cell HbSD is caused by a mutation in the gene that produces normal copies of the haemoglobin protein. This mutation causes the gene to tell the body to produce abnormal copies of haemoglobin. In the case of HbSD, one copy of the haemoglobin gene tells the body to produce haemoglobin protein “S” and the other copy of the haemoglobin gene tells the body to produce haemoglobin protein “D”.
Having parents with the haemoglobin “S” trait or the haemoglobin “D” trait is not a cause for HbSD, but it is a risk factor. In cases where one parent has the haemoglobin “D” trait and the other has the haemoglobin “S” trait, there is a 25% chance that a baby born to this couple will have HbSD. Other alternatives involve the child carrying just the haemoglobin “S” trait, just the haemoglobin “D” trait, or having completely normal haemoglobin traits.
Since genetics is such a risk factor for HbSD, people with abnormal haemoglobin traits or some form of SCD, including HbSD, may consider getting genetic screening done when trying to conceive.
Another risk factor for HbSD is being of Indian descent. The chances of having HbSD are much higher than in any other population.
Sickle cell HbSD is often diagnosed in newborns during a routine blood test. If you’re an older child or adult who was not diagnosed with sickle cell HbSD as a newborn that is now having symptoms, a doctor will use a combination of your medical history, symptoms, and a blood test to confirm your diagnosis.
Complications of sickle cell HbSD include stroke, chest pain, fever, trouble breathing, high blood pressure in the lungs, and organ damage. These complications are much less likely to affect people with sickle cell HbSD.
Treatment for sickle cell HbSD includes medication, lifestyle changes, infection prevention, and more serious measures like blood transfusions. There are currently medications that can manage pain crises and other debilitating symptoms like headache, nausea, fatigue, and fever. Eating a balanced diet, avoiding changes in altitude or places with low oxygen levels, and avoiding air travel can help manage sickle cell HbSD.
Additionally, receiving routine vaccinations and maintaining proper hand washing can help prevent infection. In some cases, a person with sickle cell HbSD may need a blood transfusion to keep them oxygenated. Their doctor may also recommend a bone marrow transplant as a last resort treatment option.